#3874: document HTMLParser.unknown_decl().
diff --git a/Doc/library/html.parser.rst b/Doc/library/html.parser.rst
index ef0ae83..c38cf2a 100644
--- a/Doc/library/html.parser.rst
+++ b/Doc/library/html.parser.rst
@@ -134,10 +134,18 @@
.. method:: HTMLParser.handle_decl(decl)
- Method called when an SGML declaration is read by the parser. The *decl*
- parameter will be the entire contents of the declaration inside the ``<!``...\
- ``>`` markup. It is intended to be overridden by a derived class; the base
- class implementation does nothing.
+ Method called when an SGML ``doctype`` declaration is read by the parser.
+ The *decl* parameter will be the entire contents of the declaration inside
+ the ``<!...>`` markup. It is intended to be overridden by a derived class;
+ the base class implementation does nothing.
+
+
+.. method:: HTMLParser.unknown_decl(data)
+
+ Method called when an unrecognized SGML declaration is read by the parser.
+ The *data* parameter will be the entire contents of the declaration inside
+ the ``<!...>`` markup. It is sometimes useful to be be overridden by a
+ derived class; the base class implementation throws an :exc:`HTMLParseError`.
.. method:: HTMLParser.handle_pi(data)